Flutter GetX - Fetching Data From OpenSea API

flutter pub get

class OpenseaModel {
  OpenseaModel({
    required this.assets,
  });
  List? assets;  OpenseaModel.fromJson(Map json) {
    assets = List.from(json['assets']).map((e) => Assets.fromJson(e)).toList();
  }
  Map toJson() {    final _data = {};
    _data['assets'] = assets!.map((e) => e.toJson()).toList();
    return _data;
  }
}
class Assets {
  Assets({
    required this.imageUrl,
    required this.name,
    this.description,
    required this.permalink,
  });
  String? imageUrl;
  String? name;
  String? description;
  String? permalink;
  Assets.fromJson(Map json) {
    imageUrl = json['image_url'];
    name = json['name'];
    description = null;
    permalink = json['permalink'];
  }
  Map toJson() {    final _data = {};
    _data['image_url'] = imageUrl;
    _data['name'] = name;
    _data['description'] = description;
    _data['permalink'] = permalink;
    return _data;
  }
}

import 'dart:convert';
import 'package:get/get.dart';
import 'package:getx_tutorials/models/opensea_model.dart';
import 'package:http/http.dart' as http;
class OpenseaController extends GetxController {
  var isLoading = false.obs;
  OpenseaModel? openseaModel;
  @override
  Future onInit() async {
    super.onInit();
    fetchData();
  }
  fetchData() async {
    try {
      isLoading(true);
      http.Response response = await http.get(Uri.tryParse(
          'https://api.opensea.io/api/v1/assets?collection=cryptopunks')!);
      if (response.statusCode == 200) {
        ///data successfully
        var result = jsonDecode(response.body);
        openseaModel = OpenseaModel.fromJson(result);
      } else {
        print('error fetching data');
      }
    } catch (e) {
      print('Error while getting data is $e');
    } finally {
      isLoading(false);
    }
  }
}

import 'package:flutter/material.dart';
import 'package:get/get.dart';
import 'package:getx_tutorials/controllers/opensea_controller.dart';
import 'package:url_launcher/url_launcher.dart';
main() {
  runApp(GetMaterialApp(home: MyApp()));
}
class MyApp extends StatelessWidget {
  OpenseaController openseaController = Get.put(OpenseaController());
 @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('opensea Api')),
        body: Obx(
      () => openseaController.isLoading.value
          ? Center(
              child: CircularProgressIndicator(),
            )
          : ListView.builder(
              itemCount: openseaController.openseaModel?.assets?.length ?? 0,
              itemBuilder: (context, index) {
                return ListTile(
                    title: Text(
                        openseaController.openseaModel?.assets![index].name ??
                            'no name'),
                    subtitle: Text(openseaController
                            .openseaModel?.assets![index].description ??
                        'no description'),
                    leading: openseaController
                                .openseaModel?.assets![index].imageUrl ==
                            null
                        ? Icon(Icons.image)
                        : Image.network(openseaController
                            .openseaModel!.assets![index].imageUrl!),
                    onTap: () {
                      _launchInBrowser(Uri.parse(openseaController
                          .openseaModel!.assets![index].permalink!));
                    });
              }),
    ));
  }
  Future _launchInBrowser(Uri url) async {
    if (!await launchUrl(
      url,
      mode: LaunchMode.externalApplication,
    )) {
      throw 'Could not launch $url';
    }
  }
}